Merchant banker and professional deal-maker Gardner Brook has different explanations for the scar on his neck. They range from the pedestrian (a fall down some stairs in downtown Brisbane), to the preposterous (he was bayoneted through the neck while on a special forces training exercise).

The trouble is, of course, that only one of those stories can be true. For those around him, Brook's life is a bit like that: a tussle between fact and fiction. The investment guru has access to deal books in London and Monaco and even to petro-dollars in Dubai. Or he does not.

But there is at least one sure thing in Brook's world. In just a few weeks, the 40-year-old will take his seat before a public inquiry to explain his role in a corruption scandal that has embroiled three former cabinet ministers and some of the wealthiest businessmen in NSW.

Gold Coast mayor Ron Clarke. Photo: Robert Rough

One question the Independent Commission Against Corruption might ask is this: Why did Brook boast of ''inside intelligence'' during a coal licence tender run by Ian Macdonald, the now disgraced former resources minister?

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It might also ask how he first met Moses Obeid, the son of Macdonald's mate Eddie Obeid, the ALP kingmaker, and what they discussed. But then, the ICAC might simply want to know one thing: how could it be that Brook, with no mining experience and just a $1 company, was issued an exploration licence worth millions?

But the problem for the ICAC will be in deciding what is true and what is not in the incredible story of Paul Gardner Brook's life.

"He was a lot of talk but I found him to be quite shady" ... Troy Dann. Photo: Ken Robertson

Certainly he has come a long way from his early days in the former gold-rush capital, Bendigo. From there, it seems he joined the army. That is what everyone who has met him agrees - though they don't know if he attended the officer's training college at Duntroon or travelled over to Perth to join the SAS. He did a business degree at La Trobe, and then moved into banking and finance. He first appears on the corporate records radar in 1997, when he set up something he called Oregon Standard Pty Ltd.

At about this time he had taken a job with an equipment finance company in Brisbane, then called ANA Capital. Its boss, Andrew Noble, had also heard the story of his military training. ''I am not sure if he was SAS, but he had a military background - it was on his resume,'' he said. ''As far as we were told, he did serve in Timor.

''Our objectives didn't see eye to eye and he ended up resigning probably about 18 months after he started,'' Noble says.

Moses Obeid.

''I came in one day the weekend after he resigned and he was in here downloading files.''

Brook moved to Melbourne and into business in 1999 with some fast-moving finance guys in Melbourne. He fitted in perfectly. ''Slick'' was how one described him. Another said he was ''confident to the point of arrogance'', but certainly he could talk the talk. He had a good head for figures and he knew how to give a presentation.

Riverside Capital's owner, Steven Goldberg, was so impressed with him that he gave him a start. The way he tells it, he expected Brook to bring in big corporate deals. ''I got him set up in his own entity, GBM. We had 23 people and $350 million a year in loans. We set up GBM capital and I said, here, you run that.''

The idea was that Brook would find distressed companies that could be turned around or other smart companies to pour money into and then Goldberg and his private equity contacts would stump up the money; everyone would get fees along the way. But Brook worked on only one deal with a plastics manufacturing company before things turned pear-shaped.

He and Goldberg blame each other on the falling out; each say they were left short-changed.

Those close to Brook describe a frenetic lifestyle of entertaining clients and heavy drinking that meant he was out most nights of the week into the small hours. Although he jetted overseas regularly and dressed sharply, often there was little money around; for several years, during 2008 and 2009, when he was doing deals with mining companies in Sydney, he lived in a Potts Point flat that an associate of his said was bare except for a bed, chair and fridge.

Another person tells a story from a social gathering about Brook's fantasies: ''He starts crying, and the girls start asking him 'what's wrong?' He said, this was the anniversary of a mission I oversaw in a 'Black Hawk down' kind of [scenario]. [He was saying] I was in charge of a platoon of US SAS rangers and as they went down the rope from the helicopter they were shot and set upon by the enemy and five of the Americans died. What made him cry was it was not only the anniversary but one of the widows had called him to say, 'it is not your fault, Gardner.' ''

Brook was also volatile. At one Christmas party in Melbourne about 10 years ago, which he attended with his wife, he headbutted Goldberg's accountant after a drunk karaoke session. After singing with their arms around each other, Brooks accused the man of letting his hand slip down her back to her bottom.

He and his wife moved back to Brisbane and he fell in with the long-standing Gold Coast mayor Ron Clarke. Brook helped Clarke with a sprawling island resort called Couran Cove on South Stradbroke Island (though it is not clear exactly what he did), and he also worked on one of Clarke's many successful election campaigns. ''He was very effective and very good,'' Clarke says.

Nonetheless they parted ways after the campaign, and after another stint in Melbourne and the breakdown of his marriage, Brook took a job in Singapore with Pan-Asia Presidio Capital.

While there, he made a contact who gave him what should have been a golden ticket to return to Sydney. In the early months of 2008, Brook was appointed as a vice-president for Lehman Brothers' Australian subsidiary, Grange Securities. Suddenly he had a balance sheet of several million dollars. He had cachet.

On September 15, when Lehman Brothers collapsed, everything changed. Four weeks later Brook was out of a job. He began trawling for work. In 2010, he started a company with Troy Dann, the TV star of Outback Adventures. Dannbrook Pty Ltd was to be an agricultural fund that would invest in bush ventures the banks were ignoring. ''We talked about a project that could help farmers,'' Dann says. ''He was a lot of talk but I found him to be quite shady and I didn't go forward with him because I didn't want to be associated with him.''

Brook also tried starting up another venture capital fund with former solicitor Hector Ekes, a close friend of Moses Obeid, but this too soured. Ekes ended the relationship after Brook allegedly used Ekes's $50,000 to fly to Monaco with his girlfriend and shop at Harrods in London.

Brooks said he needed to fly there urgently to find the finance he needed to rescue the one big deal he had been working on while at Lehmans - a bid for a coal exploration licence that could be worth tens of millions of dollars.

He had secured a retainer with one bidder, Monaro Mining, by promising he had the inside running on the tender. And when Monaro decided it couldn't afford to follow the bid through, it was Brook himself who was awarded an exploration licence for a mining tenement now called Ferndale. It is worth tens of millions of dollars. His business partner in the venture was Andrew Kaidbay, a long-standing adviser to the Obeid family.

But it seems Brook just can't take a trick. First Lehmans collapsed. And now, his coal deal is about to be picked over by David Ipp, QC, the state's current corruption-busting inquisitor. Many are waiting to see whether even he can get to the bottom of Brook's story.

In the meantime, however, Fairfax Media has at least been able to get an answer about what happened to his neck. How did he get that raised, livid scar behind his ear, we asked. Was it a glassing (another of his explanations)? Or was it the bayonet?

He paused for a moment on the phone from Singapore and said that, in fact, he has two scars on his neck.